#include "kernel.h"
#include "string.h"
#include "stdarg.h"

#define is_digit(c) ((c) >= '0' && (c) <= '9')

// 这里为什么要传指针的指针   是因为需要在这个函数里修改指针
static int skip_atoi(const char **s)
{
    int i = 0;
    while (is_digit(**s))
    {
        i = i * 10 + (**s - '0');
        (*s)++;
    }
    return i;
}

#define ZEROPAD 1
#define SIGN 2
#define PLUS 4
#define SPACE 8
#define LEFT 16
#define SPECIAL 32
#define SMALL 64

#define do_div(n, base) ({ \
    int __res; \
    __asm__("div %4": "=a"(n), "=d"(__res): "0"(n), "1"(0), "r"(base)); \
    __res;})

static char* number(char* str, long long num, long long base, int size, int precision, int type)
{
    char c, sign, tmp[36];
    const char* digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int i;

    if (type & SMALL) 
    {
        digits = "0123456789abcdefghijklmnopqrstuvwxyz";
    }
    
    if (type & LEFT)
    {
        type &= ~ZEROPAD;
    }

    if (base < 2 || base > 36)
    {
        return 0;
    }
    
    c = (type & ZEROPAD) ? '0' : ' ';
    if (type & SIGN && num < 0)
    {
        sign = '-';
        num = -num;
    }
    else
    {
        sign = (type & PLUS) ? '+' : ((type & SPACE) ? ' ' : 0);
    }
    
    if (sign)
    {
        size--;
    }
    
    if (type & SPECIAL)
    {
        if (base == 16)
        {
            size -= 2;
        } 
        else if (base == 8)
        {
            size -= 1;
        }
    }
    
    i = 0;
    if (num == 0)
    {
        tmp[i++] = '0';
    }
    else while (num != 0)
    {
        tmp[i++] = digits[do_div(num, base)];
    }
    
    if (i > precision)  
    {
        precision = i;
    }

    size -= precision;

    if (!(type & (ZEROPAD | LEFT)))
    {
        while (size-- > 0)
        {
            *str++ = ' ';
        }
    }
    
    if (sign)
    {
        *str++ = sign;
    }
    
    if (type & SPECIAL)
    {
        if (base == 8)
        {
            *str++ = '0';
        }
        else if (base == 16)
        {
            *str++ = '0';
            *str++ = digits[33];
        }
    }
    
    if (!(type & LEFT))
    {
        while (size-- > 0)
        {
            *str++ = c;
        }
    }

    while (i < precision--)
    {
        *str++ = '0';
    }
    
    while (i-- > 0)
    {
        *str++ = tmp[i];
    }
    
    while (size-- > 0)
    {
        *str++ = ' ';
    }
    return str;
}

int vsprintf(char* buf, const char* fmt, va_list args)
{
    int len;
    int i;
    char* str;
    char* s;
    int* ip;

    int flags;

    int field_width;
    int precision;

    int qualifier;

    for (str = buf; *fmt; fmt++)
    {
        if (*fmt != '%')
        {
            *str++ = *fmt;
            continue;
        }
        
        flags = 0;
    repeat:
        fmt++;
        switch (*fmt) 
        {
        case '-': flags |= LEFT; goto repeat;
        case '+': flags |= PLUS; goto repeat;
        case ' ': flags |= SPACE; goto repeat;
        case '#': flags |= SPECIAL; goto repeat;
        case '0': flags |= ZEROPAD; goto repeat;
        }

        field_width = -1;
        if (is_digit(*fmt))
        {
            field_width = skip_atoi(&fmt);
        }
        else if (*fmt == '*')
        {
            field_width = va_arg(args, int);
            if (field_width < 0)
            {
                field_width = -field_width;
                flags |= LEFT;
            }
            fmt++;
        }
        
        precision = -1;
        if (*fmt == '.')
        {
            fmt++;
            if (is_digit(*fmt))
            {
                precision = skip_atoi(&fmt);
            } else if (*fmt == '*')
            {
                precision = va_arg(args, int);
                fmt++;
            }
            if (precision < 0)
            {
                precision = 0;
            }
        }

        qualifier = -1;
        if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L')
        {
            qualifier = *fmt++;
        }
        
        switch (*fmt)
        {
        case 'c':
            if (!(flags & LEFT))
            {
                while (--field_width > 0)
                {
                    *str++ = ' ';
                }
            }

            *str++ = (unsigned char) va_arg(args, int);
            while (--field_width > 0)
            {
                *str++ = ' ';
            }
            break;
        case 's':
            s = va_arg(args, char*);
            len = strlen(s);
            if (precision < 0)
            {
                precision = len;
            }
            else if (len > precision)
            {
                len = precision;
            }

            if (!(flags & LEFT))
            {
                while (len < field_width--)
                {
                    *str++ = ' ';
                }
            }
            for (i = 0; i < len; i++)
            {
                *str++ = *s++;
            }
            
            while (len < field_width--)
            {
                *str++ = ' ';
            }
            break;
        case 'o':
            str = number(str, va_arg(args, unsigned long long), 8, field_width, precision, flags);
            break;
        case 'p':
            if (field_width == -1)
            {
                field_width = 8;
                flags |= ZEROPAD;
            }
            str = number(str, (unsigned long) va_arg(args, void*), 16, field_width, precision, flags);
            break;
        case 'x':
            flags |= SMALL;
        case 'X':
            str = number(str, va_arg(args, unsigned long long), 16, field_width, precision, flags);
            break;
        case 'd':
        case 'i':
            flags |= SIGN;
        case 'u':
            str = number(str, va_arg(args, unsigned long long), 10, field_width, precision, flags);
            break;
        case 'n':
            ip = va_arg(args, int *);
            *ip = str - buf;
            break;
        default:
            if (*fmt != '%')
            {
                *str++ = '%';
            }
            if (*fmt)
            {
                *str++ = *fmt;
            }
            else
            {
                --fmt;
            }
            break;
        }
    }
    
    *str = '\0';
    return str - buf;
}